3 Answers
3

Bread that is cut into pieces retains its status of bread (i.e. Hamotzi) no matter how small the pieces get. So if you or anyone would cut the bread and then bake it again, it wouldn't matter and it would still be Hamotzi [unless you cut it less than a K'zayis an cook it in water to a certain degree... but not so practical]

However, there's a famous shitah (R' Shlomo Zalman Auerbach) that holds that if companies make croutons - even though it's bread at an intermediate stage - since the end product will be croutons (which should be Mezonos for its own reasons) the entire product is Mezonos. In other words, it doesn't get a status of bread if the end-game is to make it into something else.

So in short:

If it's homemade from bread it's Hamotzi (even in Salad - because it cannot become a Taful)

If it's manufactured (like the way you say - i.e. made from bread) we have the above Machlokes

If it's deep fried then it would appear everyone agrees it's mezonos.

If it's a "yellow-type" crouton (i.e. deep fried and no where near bread) it's a clearcut Mezonos.

I'm not sure about the one's in instant soup (I've never personally come across them), but is seems they're like the second type mentioned above.